Can I programmatically activate an Input Axis?

Here is the thing,

I have a default character controller, and I want to control it using a set of GUI Textures that I have included in the screen. So when I detect the screen is being touched I can then proceed to move the character. The thing is that, when I detect such event I want to artificially activate an Input Axis so the Character Itself reads the signal and translates itself

It there a way to do that?

Thanks!

Checkout the AngryBots demo for an example of using on-screen joysticks.